1. Technical Field
The present invention relates to geometric dimensioning and tolerancing. More specifically, the invention relates to graphical representation of features and their related geometric dimensioning and tolerancing constraints.
2. Description of Related Art
The ASME Y14.5 M geometric dimensioning and tolerancing standard (Y14.5) provides a symbolic language with which designers can specify design requirements for mechanical parts and assemblies. The range of tolerance types and shapes, combined with the concept of a fully or partially constrained datum reference frame, gives the designer complete control over the product definition. GD&T (Geometric Dimensioning & Tolerancing) symbols are combined to create a Feature Control Frame (FCF) that defines a specific part requirement.
The large number of permissible permutations/combinations of symbols leads to a problem for use of this symbolic design requirements language. Specifically, it is often difficult to comprehend exactly what requirement is imposed by a particular FCF construct. This is particularly true for people other than the original designer, such as the machinist who must manufacture parts conforming to the design requirement and the quality control specialist who must measure parts to verify conformance to the design requirements. Tolerance zone shapes, coupled with the concept of a partially constrained datum reference frame lead to complex tolerance zone boundaries, based on the nominal part structure that may change size, location or orientation depending on the exact combination of symbols used.
In some instances, the designer is also unaware of the particular FCF construct. Specifically, a novice designer may include dimensioning and tolerancing that is unnecessary, which leads to increased cost of manufacture and testing.
The conventional art includes products that limit the display of GD&T definition information to the display of degrees of freedom of the datum reference frame defined in the FCF. This is conventionally done by drawing a trihedral symbol to show the x-, y-, and z-axes of the datum reference frame and animating that trihedral symbol to show which degrees of freedom are unconstrained. However, this conventional arrangement does not display tolerance zones to the user.
There also exist training aides that illustrate the meaning of a subset of all possible constructs using a predefined example part, but these systems are deficient in that the cases that they illustrate are fixed and often bear no resemblance to the part to be manufactured or the preferred FCF of the part being designed.
Thus, there is a need in the art for an improved graphical representation feature with associated geometric dimensioning and tolerancing.